Bottom Line:
It has been hypothesized that suppressed nocturnal melatonin production is associated with an increased risk of breast cancer, but results from several small prospective studies of the association have been inconclusive.In summary, we found no evidence that 6-sulfatoxymelatonin level in a first-morning urine sample was associated with breast cancer risk among British women.Further data are needed to confirm this association.

ABSTRACTIt has been hypothesized that suppressed nocturnal melatonin production is associated with an increased risk of breast cancer, but results from several small prospective studies of the association have been inconclusive. We examined the association between nocturnal melatonin and breast cancer risk in a case-control study nested within the Guernsey III Study, a British prospective cohort study (1977-2009). Concentrations of 6-sulfatoxymelatonin were measured in prediagnostic first-morning urine samples from 251 breast cancer cases and 727 matched controls. Conditional logistic regression models were used to calculate odds ratios for breast cancer in relation to 6-sulfatoxymelatonin level. No significant association was found between 6-sulfatoxymelatonin level and breast cancer risk, either overall (for highest third vs. lowest, multivariable-adjusted odds ratio = 0.90, 95% confidence interval: 0.61, 1.33) or by menopausal status. However, in a meta-analysis of all published prospective data, including 1,113 cases from 5 studies, higher 6-sulfatoxymelatonin levels were associated with lower breast cancer risk (for highest fourth vs. lowest, odds ratio = 0.81, 95% confidence interval: 0.66, 0.99). In summary, we found no evidence that 6-sulfatoxymelatonin level in a first-morning urine sample was associated with breast cancer risk among British women. However, overall the published data suggest a modest inverse association between melatonin levels and breast cancer risk. Further data are needed to confirm this association.

KWT302F1: Correlations between 6-sulfatoxymelatonin concentrations in first-morning urine samples and 24-hour urine samples among 256 control participants from the Guernsey Study, 1977–2009.

Mentions:
The levels of 6-sulfatoxymelatonin (adjusted for creatinine) in first-morning urine samples (measured for the current study) and 24-hour urine samples (measured previously) were moderately correlated (based on 256 controls, r = 0.66, P < 0.0001) (Figure 1). When control participants were grouped into thirds based on the distribution of 6-sulfatoxymelatonin in first-morning and 24-hour urine samples (Table 2), 58% of participants were categorized into the same third (weighted κ = 0.49, P < 0.001), with a clear increasing trend in first-morning 6-sulfatoxymelatonin levels across increasing categories of 24-hour 6-sulfatoxymelatonin (P < 0.0001).Table 2.

KWT302F1: Correlations between 6-sulfatoxymelatonin concentrations in first-morning urine samples and 24-hour urine samples among 256 control participants from the Guernsey Study, 1977–2009.

Mentions:
The levels of 6-sulfatoxymelatonin (adjusted for creatinine) in first-morning urine samples (measured for the current study) and 24-hour urine samples (measured previously) were moderately correlated (based on 256 controls, r = 0.66, P < 0.0001) (Figure 1). When control participants were grouped into thirds based on the distribution of 6-sulfatoxymelatonin in first-morning and 24-hour urine samples (Table 2), 58% of participants were categorized into the same third (weighted κ = 0.49, P < 0.001), with a clear increasing trend in first-morning 6-sulfatoxymelatonin levels across increasing categories of 24-hour 6-sulfatoxymelatonin (P < 0.0001).Table 2.

Bottom Line:
It has been hypothesized that suppressed nocturnal melatonin production is associated with an increased risk of breast cancer, but results from several small prospective studies of the association have been inconclusive.In summary, we found no evidence that 6-sulfatoxymelatonin level in a first-morning urine sample was associated with breast cancer risk among British women.Further data are needed to confirm this association.

ABSTRACTIt has been hypothesized that suppressed nocturnal melatonin production is associated with an increased risk of breast cancer, but results from several small prospective studies of the association have been inconclusive. We examined the association between nocturnal melatonin and breast cancer risk in a case-control study nested within the Guernsey III Study, a British prospective cohort study (1977-2009). Concentrations of 6-sulfatoxymelatonin were measured in prediagnostic first-morning urine samples from 251 breast cancer cases and 727 matched controls. Conditional logistic regression models were used to calculate odds ratios for breast cancer in relation to 6-sulfatoxymelatonin level. No significant association was found between 6-sulfatoxymelatonin level and breast cancer risk, either overall (for highest third vs. lowest, multivariable-adjusted odds ratio = 0.90, 95% confidence interval: 0.61, 1.33) or by menopausal status. However, in a meta-analysis of all published prospective data, including 1,113 cases from 5 studies, higher 6-sulfatoxymelatonin levels were associated with lower breast cancer risk (for highest fourth vs. lowest, odds ratio = 0.81, 95% confidence interval: 0.66, 0.99). In summary, we found no evidence that 6-sulfatoxymelatonin level in a first-morning urine sample was associated with breast cancer risk among British women. However, overall the published data suggest a modest inverse association between melatonin levels and breast cancer risk. Further data are needed to confirm this association.